IisShield is an IIS isapi filter preventing any known and unknown attacks from disrupting IIS. The preventive approach of IisShield is an added value preventing IIS from even trying to interpret requests trying to break-in. With a detailed logging engine, IisShield helps IIS administrators to know in advance and protect IIS from known or unknown HTTP attacks that flow over the Internet.
Comment : It's better than URLscan and it's Free
Source : www.kodeit.org